Number of acyclic quaternary ammonium ions with n carbon atoms.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =18a(5) =42a(6) =109a(7) =269a(8) =691a(9) =1759a(10) =4542a(11) =11733a(12) =30559a(13) =79743a(14) =209136a(15) =549959a(16) =1451178a(17) =3838925a(18) =10182703a(19) =27069940a(20) =72121696a(21) =192527888a(22) =514908269a(23) =1379454526a(24) =3701556642a(25) =9947456861a(26) =26770280299a(27) =72138803942a(28) =194638086892a(29) =525773470041